z6 + hf tranny

i have an 89 crx hf with z6 and a 90 si trans. the tanny is at the point now that im just going to replace it. considering that almost all of my driving is to and from school (around 250 miles round trip) i thought that an hf tranny would be nice to get a little better mileage and to quiet things a bit. will any 89-91 hf trans just bolt in or is there going to be anything else that will need changed.

also some people have told me not to do this because the tranny would be a weak point in the drivetrain with this motor while others have said it will handle it just fine. is that anything to worry about

A hf transmission should put you around the 2000-2500 rpm range when crusing the interstate. 50-55mph in first gear... Personally i wouldnt think it would be any fun at all to have a HF transmission unless youre putting out the power to fully take advantage of the stretched out gearing....about 220mph, who wants to do that in a civic? According to this calculator anyways

go with the HF. I have a DOHC ZC on my 89 hf and long trips are awesome. nothing like making 80 MPH @ 2500 RPM. The tranny will handle the power, but forget about taking off fast. On the trade off you will get great MPG. Mine with some problem I can't figure out yet, makes 47mpg on highway. just remember to put it in 3rd to pass hahahaha.

has any one ever put hf 5th gear in a si trans?? one of my friends has a gsr trans w/an ls 5th gear.

also the gears in an hf are very close to the si trans just the final drive is different 2.95/3.25ca (si is 4.25)Lx/Dx trans has same gears as si but final drive is 3.88 compared to si's 4.25. now seeing this I want to use a hf trans with a si final drive you can take off fast but gears would be longer and a better 5th for freeway cruise'n